van Belkum A, Homan W, Limper L, Quint W G
Diagnostic Center SSDZ, Department of Molecular Biology, Delft, The Netherlands.
Mol Biochem Parasitol. 1993 Sep;61(1):69-77. doi: 10.1016/0166-6851(93)90159-u.
Detection of genetic variation among microorganisms can be done by DNA fingerprinting using the polymerase chain reaction (PCR). Application of primers directed to polymorphic DNA leads to the amplification of DNA fragments which differ in length when different species or isolates of a single species are compared. It has been demonstrated that PCR primers resembling eukaryotic repeat motifs enable the straightforward genetic differentiation of Giardia duodenalis isolates. Depending on the repeat motif, genetic variation between cloned G. duodenalis lines could also be detected. DNA polymorphisms could also be detected by random amplification of polymorphic DNA (RAPD) analyses. When the results obtained for G. duodenalis are compared to those found for another protozoan parasite, Naegleria fowleri, clear differences are encountered. In contrast to the findings for G. duodenalis, the repeat motif primers did not allow the discrimination of 'N. fowleri isolates. Apparently, as determined by this PCR-mediated genotyping, genetic variation occurs in G. duodenalis with increased frequency at the isolate level as compared to N. fowleri. The possible implications of this observation for clonality or the definition of a species in protozoan parasites will be discussed.
微生物之间遗传变异的检测可通过使用聚合酶链反应（PCR）的DNA指纹图谱技术来完成。针对多态性DNA设计的引物，在比较不同物种或单一物种的不同分离株时，会导致长度不同的DNA片段扩增。已经证明，类似于真核生物重复基序的PCR引物能够直接对十二指肠贾第鞭毛虫分离株进行遗传分化。根据重复基序，也可以检测克隆的十二指肠贾第鞭毛虫株系之间的遗传变异。DNA多态性也可以通过随机扩增多态性DNA（RAPD）分析来检测。当将十二指肠贾第鞭毛虫的结果与另一种原生动物寄生虫福氏耐格里阿米巴的结果进行比较时，会发现明显差异。与十二指肠贾第鞭毛虫的结果相反，重复基序引物无法区分福氏耐格里阿米巴分离株。显然，通过这种PCR介导的基因分型确定，与福氏耐格里阿米巴相比，十二指肠贾第鞭毛虫在分离株水平上遗传变异的发生频率更高。将讨论这一观察结果对原生动物寄生虫克隆性或物种定义的可能影响。
